Reverse pulse filter cleaning systems are well known and different systems have control valves with particular attributes which provide different degrees of cleaning efficiencies for particular applications.
Generally, it is desirable that the valve which controls the pulse of air is able to open rapidly and should have a clear flow passage through the valve in order that the pulse of high pressure air which impacts the filter defines a relatively sharp peaked pressure wave which will in turn provide the most effective cleaning or particle dislodgement force.
The rapidity with which the valve opens and closes leads to improved efficiency in the system. A valve that closes slowly, for example, will tend to waste high pressure air, adding to the cost of running the cleaning system. Likewise, a valve which opens slowly will tend to produce a somewhat dissipated peak pulse which will be less effective in cleaning the filter.
Valves which are used in filter cleaning operations need to be serviced or maintained from time to time. Also, in a typical application there are a large number of valves which need to be fitted and, accordingly, the speed with which valves can be fitted, and removed and replaced for maintenance purposes, is relatively important. Thus, the mounting arrangement should preferably be relatively straightforward to employ but, whatever mounting arrangement is used, the efficiency of the valve should not be compromised because of the particular mounting arrangement that has been selected.
Typically, high pressure air which is used to provide the reverse pulse is conveyed or supplied in a conduit or tank to which the individual valves are mounted. The tank will normally be of sufficient capacity to enable individual valves to operate in the required sequence without decreasing the efficiency of the pulses due to insufficient air capacity. Thus, most systems employ a relatively large capacity tank to which individual valves are mounted, each valve being located above a filter element to be cleaned. In order to safely contain the pressurised air, such tanks are typically of cylindrical configuration, and thus the individual valves need to be mounted to a curved wall which adds to the difficulty of the mounting arrangement for the individual valves on the tank. Alternatively, a valve may be provided to allow for cleaning of an entire row of filters, whereby the filters are suspended below a blow tube which is typically in the form of a pipe having a series of holes with each hole corresponding to a filter element so as to distribute cleaning air into each of the filters.